After I hit about 25-30 puzzles, it sometimes happens that I finish a puzzle and I can't hit the -> (Next) button. It's the light green color and not clickable.
Training (custom) puzzles count towards the daily puzzle limits. With Gold you may be on a version of the plan with a limit of 25 per day.
https://support.chess.com/article/4566-september-1st-plan-changes
After I hit about 25-30 puzzles, it sometimes happens that I finish a puzzle and I can't hit the -> (Next) button. It's the light green color and not clickable.